"Sight Dependent Systems" semiphore, lamps, heliograph, things like that.
Quote:
Originally Posted by Bruce MacMillan
I have a document called "armoured & infantry divisional signal regiments" that probably dates from the late 1940s. A paragraph states "Sigs provides three main means of comms". They then refer to WRLS, LINE & SDS. WRLS I take is wireless, Line is telephony but what is SDS? Motorcycle?
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